1. Field of the Invention
This invention relates to a recording device of a type, in which liquid is discharged from a nozzle or nozzles by the action of heat energy. More particularly, the invention is concerned with a recording device of improved liquid discharge efficiency, discharge response, easiness in manufacture, and so forth.
2. Description of the Prior Art
So-called non-impact recording methods have recently drawn public attention in that the noise at the recording could be reduced to a negligible order. Among these particularly important is the so-called ink jet recording method which permits high-speed recording on a plain paper without necessity for particular fixing treatment. In this field, there have been proposed various approaches including those already commercialized and those still under development.
Such ink jet recording, in which droplets of a liquid recording medium, or usually called "ink", are made to spatter and be deposited on a recording member to achieve the recording, can be classified into several processes according to the method of forming the droplets and also to the method of controlling the direction of flight of the droplets.
A process is disclosed, for example, in the U.S. Pat. No. 3,060,429 (Teletype process), in which the liquid droplets are generated by electrostatic pull, and the droplets thus generated on demand are deposited onto a recording member with or without an electric-field control on their flight direction.
More specifically the electric-field control is achieved by applying an electric field between the liquid contained in a nozzle having an orifice and an accelerating electrode, thereby causing the liquid to be ejected from the orifice and to spatter between x-y deflecting electrodes which are so arranged as to be capable of controlling electric field in accordance with the recording signals, and thus selectively controlling the direction of flight of droplets according to variations in the strength of electric field to obtain deposition at desired positions.
While this type of recording head is simple in its construction, the system as a whole is not necessarily simple, hence there are various disadvantages inherent in it such that high degree of technique and precision are required of electrical controls in generation and spattering direction of droplets, and further that the multi-orifice arrangement of the recording head, which is indispensable in the high speed recording operation, is difficult.
Another process is disclosed, for example, in the U.S. Pat. No. 3,596,275 (Sweet process) and in the U.S. Pat. No. 3,298,030 (Lewis and Brown process), in which flow of liquid droplets having controlled electrostatic charges is generated by continuous vibration and is made to fly between deflecting electrodes forming a uniform electric field therebetween to obtain a recording on a recording member.
More specifically, in this process, a charging electrode which receives recording signals is provided in front of, and at a certain distance from, the orifice of a nozzle constituting a part of a recording head equipped with a piezo vibrating element, and a pressurized liquid is supplied into the nozzle, while an electric signal of a determined frequency is applied to said piezo vibrating element to cause mechanical vibration thereof, thereby causing the orifice to emit a flow of liquid droplets. As the emitted liquid is charged by electrostatic induction by the abovementioned charging electrode, each droplet becomes provided with a charge corresponding to the recording signal. The droplets having such controlled charges are subjected to deflection corresponding to the amount of the charges during their flight through a uniform electric field between the deflecting electrodes so that only those carrying recording signals may be deposited onto the recording member.
Even this type of recording head has the essentially same defects as those in the recording head of the first-mentioned type.
Still another type of the recording head is such that liquid is discharged by mechanical vibrations to spatter it in the form of droplets. This is a "on-demand" type recording head. In this type of recording head, a volume of the liquid chamber, into which the liquid is supplied, is varied in accordance with a signal by mechanical vibrations of a piezo vibrating element, whereby the liquid is discharged in the form of droplets. Concrete construction of such recording head is disclosed in U.S. Pat. No. 3,747,120, IEEE Transaction on Industrial Applications, Vol. IA-13, No. 1, January/February, 1977, and other publications.
While such recording head is extremely simple in the construction of the system as a whole, it is not perfectly free from difficulties and problems in its construction and performances. That is, since the droplets are generated by mechanical vibrations of the piezo vibrating element, response in its high speed recording is problematical; various working problems exist in the formation of the liquid chamber, installation of the piezo vibrating element, and others; and, since miniaturization of the recording head is difficult, high density multi-orifice arrangement of the recording head with an orifice density of one or more orifices per pitch is extremely difficult, hence difficulty in the high speed recording.
As such, most of the conventional recording heads have various points of problem yet to be solved in respect of their construction, working, high speed recording, high density multi-orifice arrangement, and further the construction of the system as a whole.